This invention relates to home water supply plumbing, particularly to a system for automatically backwashing a filter each time a well pump is deactivated.
In a well water system, removal of sediment is usually effected by a filter, placed in the supply line extending between the well and a storage tank in the home. Over time, the filter becomes loaded with sediment, increasing the pressure loss through the filter, and requiring periodic cleaning or replacement of the filter element.
One way of cleaning a filter element is to backwash it, by forcing fluid backwards through the filter. There are some filter systems, in other environments, in which back-washing is done automatically, on an occasional or periodic basis. For example, U.S. Pat. No. 3,581,895 shows a filter system with an electromagnetically actuated reversing spool-type valve to control backwashing.
Not all backwashing systems require electrical actuators. Some are purely mechanical, and it has previously been realized that compressed gas can be used to cause a backwashing flow through filter media. For example, U.S. Pat. No. 3,834,535 discloses a swimming pool filter system comprising a filter containing a compressible member which expands when pump pressure is released to backwash a filter. U.S. Pat. No. 3,820,658 describes a sewage plant system having an air chamber which causes backwashing of the filter material when pumping pressure is reduced. The backwash liquid is returned to the source.
The prior patents do not provide simple devices which could be readily installed into a well water supply system, nor do they provide valving which would not only backwash a filter, but also direct backwash water to a drain, yet preventing contaminants from being siphoned into the system through the drain.